1. Field of the Invention
This invenion relates to the preparation of high V.I. lubricating oils by two-stage hydroprocessing.
2. Description of the Prior Art
The characteristics of satisfactory lubricating oils and specific types of lubricating oils are known in the art. To provide lubricating oils which can be used for known and everchanging specific purposes and have acceptable characteristics, the refining processes generally require a careful selection of the crude base stock and an elaborate combination of refining steps sufficient to produce the desired product.
It is desirable therefore to be able to supply the demands of the consumer by utilizing as broad a feed spectrum as possible and particularly less desirable feeds in a refining process which minimizes the refining steps necessary to obtain a desired valuable product such as lubricating oil of high V.I. in good yields.
It is known that improved lubricating oils can be prepared by a plural stage hydrogenation process in which lubricating oil fractions are subjected to hydrogenation under different conditions prior to the hydrogenation designed to open the naphthene rings in polycyclic naphthenes. Such a process is taught by U.S. Pat. No. 2,915,452, issued Dec. 1, 1959, to Fear which uses any suitable metallic hydrogenating catalyst in each stage, although cobalt molybdate is preferred.
This process is limited in that its feedstocks are restricted to lubricating oil fractions and the catalysts used in the second stage are insufficiently selective to give a large yield of high V.I. oil.